Desmodromic

Something (like valves) which is opened and closed by a mechanical device. In most 4-stroke engines the valves are opened by the cam, but closed by the action of the valve springs. In a desmodromic system, the valves are opened by a cam and closed by a cam or a cable. A desmodromic system is more costly and more difficult to manufacture, but the advantage is more precise control of the valves and less valve bounce which is seen in a normal engine at high speed.